A new terminal, known as a Machine Type Communication (MTC) terminal and which is used in a communication system that includes a base station device (hereinafter, sometimes simply referred to as “base station”) and a communication terminal device (hereinafter, sometimes simply referred to as “terminal”) has recently been receiving attention. Examples of MTC terminals include smart meters, which are electrical power meters that include a wireless communication function, and vending machines that have a wireless communication function. Smart meters that include a wireless communication function transmit data on, for example, the measured electrical power usage to a base station. Vending machines that have a wireless communication function transmits, to a base station, sales information, inventory information, and the like.
Unlike mobile terminals, such as mobile phones carried by users, MTC terminals are less likely to be moved; therefore, it is not desired that the MTC terminals include a communication function that can adaptively cope with changes in the communication environment. Furthermore, when compared with a mobile terminal, an MTC terminal uses fewer types of data and a lower volume of communication data for communication. Consequently, when compared with mobile terminals, the low installation costs and communication costs of the MTC terminals are desirable.
For MTC terminals, which have the desirable above-described cost reductions, there is a conventional technology that does not need a Control Format Indicator (CFI) notification to be sent from a base station to an MTC terminal because with this technology a CFI that indicates the region size of a control channel (CCH) has a fixed value. By using a CFI with a fixed value, the MTC terminals do not need to include the function of receiving a CFI and thus there is no need to transmit the CFI from the base station; therefore, it is possible to reduce the needed installation and communication costs of the terminals.
Related-art examples are described, for example, in 3GPP TSG-RAN WG1 Meeting #72, R1-130462, St Julian's, Malta, 28 Jan.-1 Feb. 2013.
However, base stations also communicate with mobile terminals in addition to communicating with MTC terminals. Consequently, in accordance with the movement of the mobile terminals, the number of terminals accommodated by a single base station (hereinafter, sometimes referred to as the “accommodated terminal count”) continuously varies. Furthermore, in a CCH region, because control data, such as scheduling information, with respect to each terminal is transmitted, the needed CCH region size increases as the accommodated terminal count increases. Consequently, if the CCH region size, i.e., the CFI value, is small and fixed, there may be some terminals that are notified of scheduling information, and some terminals that are not notified of scheduling information when the accommodated terminal count becomes large. Accordingly, in order to prevent the occurrence of terminals that are notified of scheduling information and terminals that are not notified of scheduling information, it is conceivable to use a CCH region size, i.e., the CFI value, such that the CCH region size is large and fixed. However, if the CCH region size is large and fixed, some CCH region is wasted and the efficiency with which a CCH is used in the resource decreases when the accommodated terminal count becomes low.